Outer shell structure of scroll compressor for fuel cell

ABSTRACT

A scroll compressor for a fuel a cell which vibrates little and is compact in size. The scroll compressor includes a front housing formed integrally with a stationary scroll, a center housing molded as a unitary structure coupled to the front housing and covering at least a portion of a drive crank mechanism and a portion of a drive motor, and a rear housing coupled to the center housing and covering the rear side of the drive motor. The front housing, the center housing and the rear housing form an outer shell of the compressor. The center housing that is molded as a unitary structure helps markedly increase the rigidity as a whole, and suppresses the vibration of the scroll compressor for a fuel cell.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a scroll compressor for feeding a compressed gas (compressed hydrogen, compressed air or compressed oxygen) to a fuel cell. More specifically, the present invention relates to a scroll compressor for a fuel cell, which is compact in size and suppresses vibration in operation.

[0003] 2. Description of the Related Art

[0004] A scroll compressor, which is a kind of compressor, is highly efficient and has a short axial length, compared with other compressors, and is now finding extensive applications in such fields as household air conditioners, automotive air conditioners and the like. Recently, further, a scroll compressor has been used for feeding a compressed gas such as air (oxygen) or hydrogen (hereinafter referred to as “air” or “air and the like” for convenience) to the electrode of a fuel cell (hydrogen-oxygen type).

[0005] Generally, however, the fuel cell requires much air and the like. When the air and the like are to be fed to the fuel cell using the scroll compressor, therefore, its discharge amount must be very large, and it becomes necessary to use the scroll compressor of a large size or to operate the scroll compressor at high speed.

[0006] When the fuel cell is to be mounted on an electric vehicle and the like, however, the compressor for full cell is desired that its size is as compact as possible and it is particularly desired to decrease its diameter. Even when the fuel cells are installed and used in households, it is desired that their sizes are as compact as possible.

[0007] Further, vibration tends to increase with an increase in the operation speed. If vibration and, in particularly, vibration near a resonance frequency, could be decreased, then, a decreased amount of reinforcement may suffice, and the mounting brackets and the like parts can be designed in light and compact sizes. Accordingly, decreasing the vibration of the scroll compressor leads to realizing a scroll compressor in a compact size.

[0008] The present invention was accomplished in view of the above-mentioned circumstances, and its object is to provide a scroll compressor for a fuel cell, which features decreased vibration and a compact size.

[0009] In order to solve the above problems, the inventors have studied a housing structure suited for the scroll compressor while analyzing the vibration. FIGS. 3 and 4 illustrate an example studied. A scroll compressor 200 shown in FIG. 3 comprises a compression mechanical part A including a stationary scroll 210 and a movable scroll 220, a crank mechanical part B having a crank pin 231 a provided on a motor shaft 231 in an eccentric manner from the motor shaft 231, for orbiting the movable scroll 220, and a drive motor part C constituted chiefly by a motor for rotating the motor shaft 231.

[0010] The housing structure is of a four-split type including a front housing integral with the stationary scroll 210, a crank housing 270 covering the crank mechanical part B, a motor housing 280 covering the drive motor part C, and a rear housing 290 covering the rear side of the drive motor part C. These housing parts are fastened together by bolts.

[0011]FIG. 4 illustrates analytical results of vibration near a resonance frequency of the scroll compressor 200 (analytical method will be described later). As will be understood from FIG. 4, deviation of acceleration becomes very large at the compression mechanical part A which is a source of resonance. The acceleration also becomes great near the junction between the crank housing 270 and the motor housing 280. Being affected thereby, deviation of acceleration increases again even in the drive motor part c. It will therefore be understood that the scroll compressor as a whole vibrates to a conspicuous degree.

SUMMARY OF THE INVENTION

[0012] As a result of trial and error based on keen study and experiment, the inventors have arrived at constructing the housing as a unitary structure between the crank mechanical part and the drive motor part instead of the split structure, and have developed the scroll compressor, for a fuel cell, of the invention.

[0013] That is, the present invention is concerned with a scroll compressor for a fuel cell comprising a stationary scroll having a stationary base plate portion and a stationary spiral wall portion standing on the stationary base plate portion, a movable scroll having a movable base plate portion and a movable spiral wall portion standing on the movable base plate and arranged in mesh with said stationary scroll, a drive motor having a motor shaft, a drive crank mechanism provided in association with the motor shaft for orbiting said movable scroll, the stationary scroll and the movable scroll defining a compression chamber to compress a gas which is to be fed to an electrode of a fuel cell, a front housing integrally formed with the stationary scroll, a center housing of a unitary structure coupled to the front housing to cover at least a portion of the drive crank mechanism and a portion of the drive motor, and a rear housing coupled to the center housing and covering the rear side of said drive motor, the front housing, the center housing and the rear housing forming an outer shell of the compressor.

[0014] The center housing is integrally molded as a unitary structure to cover at least a portion of the drive crank mechanism part and a portion of the drive motor part, and exhibits increased rigidity to suppress the vibration of the whole scroll compressor for fuel cell.

[0015] Further, the front housing, which is integral with the stationary scroll, is compact in size. Besides, increased rigidity is obtained by this portion, which is more effective in suppressing the total vibration in cooperation with the center housing that is molded as a unitary structure.

[0016] It is desired that the center housing contains therein a support frame for supporting the front side of the motor shaft or for supporting the rear side of the drive crank mechanism.

[0017] By providing the support frame at a portion close to the drive crank mechanism for orbiting the movable scroll, vibration in the periphery thereof can be suppressed.

[0018] The support frame need not necessarily be formed integrally with the center housing. By forming the support frame integrally therewith, however, an increased rigidity is accomplished, which is desirable.

[0019] Though the words “front” and “rear” are used for convenience, it should be noted that these words are not intended to impose any limitation on the position for mounting the scroll compressor for a fuel cell of the invention.

[0020] The center housing that is integrally molded can be obtained by casting using a metal mold such as die casting, by casting using a sand mold, or by forging.

[0021] The fuel cell for which the scroll compressor of the invention can be employed will be those which need gases, such as hydrogen and the air, such as the alkaline aqueous solution type, solid high-molecular type, phosphoric acid type, molten carbonate type and solid electrolyte type.

[0022] Upon integrally molding the center housing, further, it need not be pointed out that the number of parts (housings, sealing members on the junction surfaces, bolts, etc.) can be decreased, the number of assembling steps can be decreased and weight can be decreased compared to those of the split structure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will now be described in more detail by way of the preferred embodiment, with reference to the accompanying drawings, in which:

[0024]FIG. 1 is a cross-sectional view illustrating a scroll compressor for a fuel cell according to an embodiment of the present invention;

[0025]FIG. 2 is a diagram illustrating the vibration modes according to the embodiment;

[0026]FIG. 3 is a cross-sectional view illustrating a scroll compressor for a fuel cell for comparison to the embodiment; and

[0027]FIG. 4 is a diagram illustrating the vibration modes for comparison.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0028] Structure of the Compressor

[0029]FIG. 1 is a cross-sectional view of a scroll compressor 100 for a fuel cell (hereinafter simply referred to as “compressor 100”) according to the preferred embodiment of the present invention. Like the scroll compressor 200 shown in FIG. 3, the compressor 100 includes a compression mechanical part A, a crank mechanical part B and a drive motor part C, and feeds the compressed air to an oxygen electrode of a fuel cell.

[0030] The compression mechanical part A includes a stationary scroll 110 and a movable scroll 120. The stationary scroll 110 includes a disk-like stationary base plate portion 11Oa, a stationary spiral wall portion 110 b standing on the stationary base plate portion 110 a, and an outer peripheral wall 110 c covering the stationary spiral wall portion 110 b. The front housing referred to by the present invention is constituted by the stationary base plate portion 110 a and the outer peripheral wall 110 c. A discharge port 111 is formed at the center of the stationary base plate portion 110 a to be continuous with the oxygen electrode of the fuel cell.

[0031] The movable scroll 120 includes a disk-like movable base plate portion 120 a and a movable spiral wall portion 120 b standing on the movable base plate portion 120 a. The stationary and movable scrolls 110 and 120 are arranged in mesh with each other to define a compression chamber 121 therebetween. An air inlet (not shown) is also formed. A bearing unit 120 c of a cylindrical shape with bottom is provided at the center on the rear side of the movable base plate portion 120 a, and bearing units 120 d of a cylindrical shape with a bottom are provided on the outer peripheral side thereof at three equally distant positions.

[0032] The crank mechanical part B includes a drive crank mechanism 140 for orbiting the movable scroll 120 and a driven crank mechanism 150 for preventing the rotation of the movable scroll 120 about its own axis. The drive crank mechanism 140 is constituted by the above-mentioned bearing unit 120 c, a crank pin 131 a of a motor shaft 131 and roller bearings 137 for supporting the crank pin 131 a. The crank pin 131 a is an eccentric portion of the motor shaft 131. The driven crank mechanism 150 is constituted by the above-mentioned bearing units 120 d, crank pins 151 a of driven crank shafts 151, and radial ball bearings 153 for supporting the crank pins 151 a. The motor shaft 131 is supported on its front side by a ball bearing 138. The driven crank shaft 151 is supported on its rear side by double row ball bearing 152. The motor shaft 131 is provided with a balance weight 131 b for canceling the moment of inertia produced by the orbiting moment of the movable scroll 120, in order to decrease the vibration.

[0033] The crank mechanical part B is accommodated in the center housing 170 together with the drive motor part C that will be described later. The crank mechanical part B and the drive motor part C are separated by a support frame 171 that is molded integrally with the center housing 170 nearly at the center thereof. The ball bearings 138 and 152 have been fitted into the support frame 171.

[0034] The drive motor part C is constituted by the center housing 170, a rear housing 190, and a drive motor 130 contained therebetween. First, the drive motor 130 is an induction motor comprising the motor shaft 131 extending axially, a rotor 133 fitted to the motor shaft 131, and a stator 134 on which a coil 135 is wound. Therefore, the drive motor 130 can be controlled, in rotational speed, by an inverter that is not shown. Further, a water jacket 171 a is provided nearly at the center of the center housing 170 covering the drive motor 130, corresponding to the position of the stator 134, so that the drive motor 130 is cooled by the cooling water.

[0035] When the compression mechanical part A is provided with the water jacket for cooling, a water passage can be easily formed in communication with that of the center housing 170 since the center housing 170 is molded as a unitary structure.

[0036] At the rear end of the drive motor 130, the rear housing 190 is secured to the center housing 170 by bolts, and a motor chamber is formed therebetween for containing the drive motor 130. At the center of the rear housing 190, the motor shaft 131 is supported by a ball bearing 139 and is hermetically sealed with a sealing 136.

[0037] When electric power is supplied to the drive motor 130, the motor shaft 131 rotates, and the movable scroll 120 orbits through the drive crank mechanism 140 in mesh with the stationary scroll 110. Then, the air is taken in from the inlet port (not shown) by the compression chamber 121 defined between the stationary scroll 110 and the movable scroll 120. As the movable scroll 120 orbits (the motor shafts rotates), the compression chamber moves from the outer periphery of the compressor to the center (of the compressor) to decrease its volume, and the compressed air is discharged through the discharge port 111.

[0038] Analysis of Vibration

[0039] In the compressor 100 of this embodiment, at least a portion of the drive crank mechanism 140 and a portion of the drive motor 130 are contained in the center housing 170 that is integrally molded as a unitary structure. The support frame 171 that serves as a partitioning wall therebetween is formed integrally with the center housing 170. The above-mentioned housing structure and the housing structure (FIG. 3) split at the center, as described earlier, were examined for their vibration characteristics. The description, here, deals with the compressor 100. The same, however, also holds for the vibration characteristics (FIG. 4) of the scroll compressor 200 described earlier.

[0040] (1) Resonance frequency

[0041] The resonance frequency of the compressor 100 (finished product) shown in FIG. 1 was found by a hammering test. In the hammering test, shock is given by using a hammer to the compressor 100 which is not in operation, and the vibration is measured by using an accelerometer pickup and is analyzed. As a result, the resonance frequency of this embodiment was 640 Hz.

[0042] (2) Mode analysis

[0043] Next, the acceleration pickups were attached to the compressor 100 at six places, and a vibration mode having a number of vibrations nearly equal to the resonance frequency found by the hammering test, was found by operating the compressor. As a result, in this embodiment, the seventh order component of rotation that appeared when the compressor is operated at a rotational speed of 5000 rpm at the discharge pressure Pd/the intake pressure Ps=0.13/0 MPa (gauge pressure) nearly corresponded to the vibration mode under the resonance condition. FIG. 2 shows a profile of vibration (acceleration) at various positions of the compressor 100.

[0044] (3) Evaluation

[0045] As will also be understood from FIG. 2, the vibration attenuated conspicuously near the portion of from the crank mechanical part B to the compression mechanical part A, from which it can be learned that a node of vibration had been formed. This is attributed to that since the center housing 170 is molded as a unitary structure, the compressor 100 as a whole exhibits increased rigidity and is vibrating as a rigid body as a whole.

[0046] The scroll compressor for a fuel cell of the present invention suppresses the vibration and realizes a compressor in a compact size, as a whole. 

1. A scroll compressor for a fuel cell, comprising: a stationary scroll having a stationary base plate portion and a stationary spiral wall portion standing on said stationary base plate portion; a movable scroll having a movable base plate portion and a movable spiral wall portion standing on said movable base plate and arranged in mesh with said stationary scroll; a drive motor having a motor shaft; a drive crank mechanism arranged in association with the motor shaft for orbiting said movable scroll; said stationary scroll and said movable scroll defining a compression chamber to compress a gas which is to be fed to an electrode of a fuel cell; a front housing integrally formed with said stationary scroll; a center housing of a unitary structure coupled to said front housing to cover at least a portion of said drive crank mechanism and a portion of said drive motor; and a rear housing coupled to said center housing and covering the rear side of said drive motor, said front housing, said center housing and said rear housing forming an outer shell of the compressor.
 2. A scroll compressor for a fuel cell according to claim 1, wherein said center housing includes a support frame for rotatably supporting the motor shaft.
 3. A scroll compressor according to claim 1, wherein said center housing entirely covers said drive motor.
 4. A scroll compressor according to claim 1, wherein said front housing covers said movable scroll.
 5. A scroll compressor according to claim 1, wherein said drive crank mechanism comprises an eccentric portion of the motor shaft, which is rotatably coupled to the movable scroll. 